• Japanese encephalitis (JE) is a viral, mosquito-borne zoonotic infection caused by the JE virus (JEV). 
  • Domestic pigs are the most important source of infection for mosquitoes that transmit JEV to humans in China, India, and Southeast Asia. 
  • In the past decade 30,000-50,000 cases of JE have been notified to WHO with 10,000 deaths.
  • JE infection may result in asymptomatic disease, unspecific febrile disease, aseptic meningitis or acute encephalitis. 
  • The case fatality rate is 30%, long-term disabilities occur in 25-50% of those surviving encephalitis. 
  • There is no specific treatment for JE. 
  • Three vaccines have been available for more than 50 years, 
    • inactivated vaccines derived from mouse brain, which effectively controlled JE in Japan and other Asian countries. They may, however, cause angioedema and generalized urticaria;
    • inactivated vaccines cultivated on primary hamster kidney cells (PHK) and 
    • live attenuated vaccine cultivated on primary hamster kidney cells.
  • Recently three new vaccines have been developed: 
    • A live-attenuated vaccine based on strain SA14-14-2 has a good safety profile, 
      effectiveness (88%-96%), and efficacy in large-scale trials (XX%).
    • Chimeric live-attenuated JE vaccine is a lyophilized formulation of a chimeric virus incorporating the structural genes (prM and E) from strain SA 14-14-2 into the non-structural genes of the yellow fever vaccine virus.
    • Inactivated JE vaccine (IC51, IXIARO) is a purified, formalin-inactivated, whole-virus vaccine grown on Vero-cell culture.